Wireless local area networks (WLAN) are increasingly utilized by organizations to provide connectivity to users. As usage increases, the number of users, the number of wireless access points, the amount of traffic, etc. all increase to the point where maximizing throughput, the amount of data that can be delivered during any given time, becomes increasingly important. However, given the dynamic nature of wireless networks, such as users moving around using mobile computing devices, users dropping in to and out of the network, etc., conflicts increasingly occur. When an access point attempts to transmit on a data channel, the channel may already be in use by another access point, creating the conflict. Generally, a “channel” describes an encoding of data for wireless transmission, such as by frequency, the permits simultaneous transmission without interference with data on other channels.
One common method for handling conflicts during transmission of wireless packet is the distributed coordination function (DCF) technique. DCF uses an algorithm at each wireless access point (WAP) to listen to the channel to determine if the channel is busy. If the channel is not busy, the WAP begins transmission. If the channel is busy, the WAP defers its transmission by a randomly generated backoff time and then attempts transmission again. This method has proven to be highly efficient in the general case at maximizing throughput for WLANs. However, DCF does not perform optimally for network that have hidden and/or exposed terminals.
A hidden terminal may be a first wireless access point that is in communication with a computing device, but is out of range of other wireless access points in communication with the computing device. Accordingly, the first wireless access point may begin transmitting, but such transmissions are not detectable by the other wireless access points such that any of the other wireless access points may simultaneously attempt to transmit causing overlapping transmissions. The problem increases significantly when networks include a large numbers of wireless access points and associated computing devices, when networks are heavily utilized, etc. as often occurs with increasing usage of mobile computing devices, etc.
An exposed terminal is a first wireless access point that is blocked from sending packets to a first computing device because of a neighboring wireless access point. In this situation the neighboring wireless access point may be transmitting to a neighbor computing device. The first computing device may be out of range of the neighboring wireless access point and the neighbor computing device may be out of range of the first wireless access point. However, if the first wireless access point is within range of the neighboring wireless access point, the transmission can be sensed by the first wireless access point and the first wireless access point will not transmit even though the transmission by both wireless access points would not create conflicts.
What is needed is a system and method for improving wireless network throughput in a network having exposed and hidden terminals.